In the production of glass containers such as bottles, jars, etc., a reservoir of molten glass is maintained in a glass feeder and is periodically released through one or more nozzles to a shear mechanism which cuts the molten glass streams into portions called gobs. The gobs are distributed by means well known in this art to the individual forming sections of the machine, generally eight in number where the glass is then given its final desired shape.
Improper cutting by the shears to form the gobs can result in the formation of defective glass articles. One such defect appears in the surface of the articles in the form of long thin stripes and these are known in the trade as cutting marks. Such defects result from an improper operation of the shears resulting in an improper cut of the gob and this is usually due to either a misalignment or improper meeting of the cutting blades. Inasmuch as these defects are not detectable until the finished ware is inspected, improper shear operation can result in a significant quanitity of defective articles before the problem is detected and corrected.
A defective cut can also result in gobs which are either too large or too small resulting in either an over consumption of glass with a consequent rise in the cost of production or in the case of too small a gob a formation of defective articles.
Known shearing mechanisms for this purpose generally include a frame which supports a pair of arms with a cutting blade at the end of each arm respectively. The arms are generally pivoted at the ends opposite the blade supporting ends and positioned to effect a cutting stroke immediately below the feeder outlets. The continuous movement of the arms is generally synchronized by a cam or gear arrangement which opens and closes the arms at a rate depending on the diameter weight and size of the gob necessary for the production of a given article. Prior art examples of this general type of shear mechanism may be found in the following U.S. patents:
Walter C. WEBBER: 2,401,994-1946 PA1 Frederick J. WYTHE: 2,812,619-1957 PA1 Clarence A. HEYNE: 3,758,286-1973 PA1 Kurt BECKER: 3,786,707-1974
Due primarily to the complexity of these mechanisms as typified in the above listed prior art patents, a series of problems have developed causing defects and irregularities in the cutting of glass gobs issuing from a feeder with a consequent loss of finished articles due to defective forming. One such problem arises when utilizing cams such as shown in the above mentioned patent to Webber and or gear mechanisms as shown in the above mentioned patents to Wythe, Heyne and Becker. Operation of the shears must be perfectly synchronized with the feeder mechanism. The main disadvantage with the cams and or gears of the prior art is the high rate of wear on these parts due to the fact that they operate continuously under conditions of high temperature and high mechanical loads. The problem of wear is such mechanisms can only be resolved by parts replacement which necessitates a complete shutdown of the entire forming operation with a consequent loss in production.
Another disadvantage of the shear mechanisms of the prior art is that whenever the production speed of the entire forming machine is to be changed depending upon the size and desired shape of the gob, it is necessary to shut down the entire machine for a considerable time in order to exchange cams and or gears to maintain the required synchronism between the shear mechanism and the feeder. The same problem arises when it is desired to change the number of feeding orifices.
A final disadvantage of the prior art shear mechanisms is the lack of flexibility to effect adjustments in the cutting arms again making it necessary to shut down the entire operation to effect such adjustments with a corresponding loss in machine output.